Question: What number makes this equation true? $615 = $
Explanation: $615 = {?}+ 544$ ${544}$ ${615}$ $+?$ Let's start by adding hundreds to ${544}$ until we get as close to ${615}$ as possible without going over ${615}$. We cannot add any hundreds without going over ${615}$. Next, let's add tens to $544$ until we get as close to ${615}$ as possible without going over ${615}$. $\begin{aligned} 544 +{10}=554\\\\ {554} +{10}= 564\\\\ {564} +{10}= 574\\\\ {574} +{10}= 584\\\\ {584} +{10}= 594\\\\ {594} +{10}= 604\\\\ {604} +{10}= 614 \end{aligned}$ If we add ${7 \text{ tens}}$, or ${70}$, we reach $614$. We cannot add any more tens without going over ${615}$. ${544}$ ${615}$ ${614}$ $+70$ Finally, how many ones should we add to $614$ to get to ${615}?$ $614 +{1}={615}$ ${544}$ ${615}$ ${614}$ $+70$ $+1$ We added ${7 \text{ tens}}$ and ${1\text{ one}}$ to ${544}$ to get to ${615}$. ${7 0}+{1}={71}$ ${544}$ ${615}$ ${614}$ $+70$ $+1$ $+71$ $615 = {71}+ 544$